Cooling system for a turbine blade

ABSTRACT

The invention relates to a blade ( 13; 14 ) for a turbine ( 10 ), comprising at least one channel ( 22 ) which is delimited by walls ( 19, 20, 21 ). An insert ( 25 ) which can be subjected to the action of a liquid coolant is inserted into at least one channel ( 22 ). According to the invention, at least one of the walls ( 19; 20 ) is provided with a number of horizontal ribs ( 24 ) which are located between the insert ( 25 ) and the wall ( 19; 20 ). Said insert ( 25 ) is provided with openings ( 27 ) through which the liquid coolant passes out of the insert ( 25 ) and between the horizontal ribs ( 24 ). The liquid coolant is therefore conducted along the wall ( 19, 20 ) and guided by the horizontal ribs ( 24 ) in order to provide improved convection cooling.

[0001] This application is the national phase under 35 U.S.C. §371 ofPCT International Application No. PCT/EP01/02755 which has anInternational filing date of Mar. 12, 2001, which designated the UnitedStates of America and which claims priority on European PatentApplication number EP 00106245.4 filed Mar. 22, 2000, the entirecontents of which are hereby incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The invention generally relates to a blade/vane. In particular,it relates to a turbine blade/vane, having at least one duct which isbounded by walls, a cooling fluid being admitted to an insert which isintroduced into at least one duct.

BACKGROUND OF THE INVENTION

[0003] A blade/vane is known from U.S. Pat. No. 5,419,039. Chambers,which extend in the direction of a longitudinal center line of theblade/vane, are formed between the insert and the walls of theblade/vane. The cooling fluid emerges from the insert into thesechambers and impinges on the walls of the blade/vane. The cooling fluidsubsequently flows along the walls and emerges through outlet openingsinto specially shaped chambers on the outside of the walls and fromthere into the surroundings. In the known blade/vane, the effect of theconvection cooling, when the cooling fluid is flowing along the walls,is only slight because the flow length is greatly limited. In addition,mixing of the cooling fluid in the chambers occurs along thelongitudinal center line of the blade/vane, so that no targeted coolingis possible.

[0004] Another blade/vane is known from WO 98/25009, which originatesfrom the same assignee. This publication describes a blade/vane withwalls which have a locally hollow configuration and through which acooling fluid flows. A high level of cooling efficiency is achievedbecause of the reduction of the wall thickness in the region of thehollow chambers. Blades/vanes with such hollow walls, however, require acomplicated casting procedure with high scrap rates and they aretherefore very expensive.

SUMMARY OF THE INVENTION

[0005] An object of an embodiment of the present invention is,therefore, to make available a blade/vane which, using a simplemanufacturing process, achieves an improvement in the cooling effect.According to an embodiment of the invention, an object may be achieved,in the case of a blade/vane, by at least one of the walls being providedwith a number of horizontal ribs. These ribs may be arranged between theinsert and the wall. Further, the insert may be provided with openings,through which the cooling fluid from the insert can enter between thehorizontal ribs.

[0006] The horizontal ribs conduct the coolant along the wall of theblade/vane and prevent a flow of the coolant in the direction of thelongitudinal center line of the blade/vane. Good convection cooling ofthe wall is, therefore, achieved. In addition, the horizontal ribsreinforce the blade/vane so that the wall thickness can be reduced. Areduction in the wall thickness leads to an increased coolingefficiency. The manufacture of the blade/vane can take place withoutcomplex cross section, using known methods. Hollow walls are notnecessary. The scrap quota is therefore substantially reduced.

[0007] In an advantageous embodiment, the insert touches the horizontalribs. The insert is supported and aligned in the desired position.

[0008] According to an advantageous development of one embodiment, thehorizontal ribs, the insert and the wall may form chambers through whichthe cooling fluid flows. A flow of the cooling fluid in the direction ofthe longitudinal center line of the blade/vane may be reliably preventedby the chambers. In addition, the cooling effect can be varied, in atargeted manner, along the longitudinal center line of the blade/vane bydifferentially admitting cooling fluid to the chambers.

[0009] In an advantageous embodiment, the openings of the insert arearranged at a first end of the chambers and outlet openings for thecooling fluid are arranged in the wall at a second end of the chambers.The cooling fluid therefore flows along the wall to be cooled over thecomplete length of the chamber, so that the convection cooling isfurther improved.

[0010] The horizontal ribs can be arranged substantially at right anglesto the longitudinal center line of the blade/vane. As an alternative, anangular position can be provided. In the case of an arrangement at rightangles with respect to the longitudinal center line, the length of thehorizontal ribs, and therefore of the chambers, is minimized. Theangular position permits an increase in the length of the chambers and,therefore, further improved convection cooling.

[0011] The insert is advantageously closed at one end. In this case, thecooling fluid is only supplied from the other end of the insert.Emergence of the cooling fluid through the end facing away from thesupply end is prevented, so that the cooling efficiency is increased. Asan alternative, the cooling fluid can be supplied from both ends.

[0012] According to an advantageous embodiment, turbulators are used toreinforce the wall and merge into one another and into the horizontalribs. By this, a substantial increase in the stiffness is achievedwithout additional material. For the same strength of the blade/vane,the wall thickness can be further reduced. Good heat exchange betweenthe walls and the cooling fluid is achieved at the same time. The resultis, therefore, a high cooling efficiency and a high overall efficiency.

[0013] The reinforcement of the wall does not only occur in the regionof an individual turbulator. A large-area reinforcement is, in fact,provided by the connection of the turbulators to one another. Theturbulators have, advantageously, a straight configuration. The use ofstraight turbulators permits a high level of reinforcement, inconjunction with simple manufacture.

[0014] According to an advantageous embodiment, the turbulators arearranged in such a way that, together with the horizontal ribs, theyform recesses adjacent to one another in the form of polygons, inparticular triangles or rhombuses. The inside of the wall is providedwith a honeycomb structure. The individual polygons or honeycombsrespectively form a closed cross section with high load-bearingcapability and mutually support one another. A substantial increase inthe stiffness can be achieved.

[0015] In an advantageous development, the wall thickness of the wall isreduced, at least in the region between the turbulators. This reductionin the wall thickness is made possible because the turbulators effect areinforcement of the wall. Due to the reduction in the wall thickness,the cooling efficiency is further increased. In this arrangement, theturbulators can be advantageously used as metal feed ducts during thecasting of the blade/vane. The honeycomb structure can therefore beconveniently manufactured.

[0016] The blade/vane according to an embodiment of the invention can beconfigured as guide vanes or as rotor blades of a turbomachine.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The invention is described in more detail below using embodimentexamples, which are diagrammatically represented in the drawing. Thesame designations are used for similar or functionally identicalcomponents throughout. In the drawings:

[0018]FIG. 1 shows a longitudinal section through a turbomachine;

[0019]FIG. 2 shows a perspective, exploded representation of ablade/vane;

[0020]FIG. 3 shows an end view onto the inside of a wall of theblade/vane;

[0021]FIG. 4 shows a section along the line IV-IV in FIG. 3;

[0022]FIG. 5 shows a section along the line V-V in FIG. 3;

[0023]FIG. 6 shows a view similar to FIG. 3 in a second embodiment;

[0024]FIG. 7 shows a diagrammatic representation of an insert in a firstembodiment; and

[0025]FIG. 8 shows a view similar to FIG. 7 in a second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026]FIG. 1 shows a longitudinal section through a turbomachine in theform of a turbine 10 with a casing 11 and a rotor 12. The casing 11 isprovided with guide vanes 13 and the rotor 12 is provided with rotorblades 14. In operation, fluid flows through the turbine 10 in the arrowdirection 15, this fluid flowing along the guide vanes 13 and rotorblades 14 and setting the rotor 12 into rotation about a center line 16.

[0027] In many applications, the temperature of the fluid is relativelyhigh, particularly in the region of the first blading row (shown on theleft in FIG. 1). For this reason, a cooling system is provided for theguide vanes 13 and rotor blades 14. The flow of the cooling fluid isdiagrammatically indicated by the arrows 17, 18.

[0028]FIG. 2 shows, diagrammatically, an exploded representation of aguide vane 13. The guide vane 13 has curved outer walls, 19, 20. Theinternal space located between the outer walls 19, 20 is subdivided intoa total of three ducts 22 by means of two separating walls 21. An insert25 is inserted into each of the ducts 22. For better representation, theinsert of the central duct 22 is not shown.

[0029] The two outer walls 19, 20 are provided with a number ofhorizontal ribs 24 in each of the ducts 22. The horizontal ribs 24extend along the walls 19, 20 and extend as far as the separating walls21. Turbulators 23 are arranged between the horizontal ribs 24. Theinserts 25 touch the horizontal ribs 24.

[0030] The cooling fluid, in particular cooling air, is supplied to aninternal space 26 of the inserts 25. The inserts 25 are provided with anumber of openings 27 through which the cooling fluid emerges into theintermediate space between the outer walls 19, 20 and the insert 25. Thecooling fluid subsequently flows along the outer walls 19, 20 as far asoutlet openings 28 in the walls 19, 20. This flow is diagrammaticallyindicated by the arrow 30. In this arrangement, the openings 27 of theinserts 25 are arranged at a distance from the outlet openings 28 of theouter walls 19, 20. In the exemplary embodiment represented, the outletopenings 28 form substantially straight rows 29.

[0031] The cooling fluid emerging from the inserts 25 first impinges onthe outer walls 19, 20, causing impingement cooling there. Itsubsequently flows along the outer walls 19, 20 as far as the outletopenings 28, so that a convection cooling is achieved. After emergingfrom the outlet openings 28, a film of the cooling fluid forms on theoutside of the outer walls 19, 20, so that film cooling is likewise madeavailable. This provides a substantially improved cooling.

[0032] The leading edge of the guide vane 13 represented to the left inFIG. 2 is additionally provided with direct impingement cooling. Forthis impingement cooling, the insert 25 has further openings 36, whichare arranged directly behind the leading edge of the guide vane 13. Thecooling medium emerges directly via these openings 36 and providesspecific cooling of the leading edge of the guide vane 13.

[0033] The associated insert 25 is also provided with a further opening37 in the region of the trailing edge of the guide vane 13. Through thisopening 37, cooling fluid emerges directly into a narrow gap 38 betweenthe outer walls 19, 20 and effects film cooling there. FIGS. 3 to 5 showmore precise details of the inside of the outer wall 19. The horizontalribs 24 extend substantially at right angles to the longitudinal centerline 31 of the guide vane 13. They are arranged parallel to one another.Straight turbulators 23 are arranged between the horizontal ribs 24 andthese turbulators 23 merge into one another and into the horizontal ribs24.

[0034] The leading edge 33 of the horizontal ribs 24 merges into theseparating wall 21 in the case of the central duct 22. In the case ofthe left-hand duct 22 in FIG. 2, the leading edge 33 is arranged at adistance relative to the outlet openings 28 which are furthest forward.

[0035] Each two horizontal ribs 24, together with the outer wall 19 andthe insert 25, bound a chamber 32. The cooling fluid emerges through theopenings 27 of the insert 25 into this chamber 32. It subsequentlyflows, as shown by the arrow direction 30, to the outlet openings 28. Inthis arrangement, the openings 27 are arranged at one end of the chamber32 and the outlet openings 28 are arranged at the other end. Thismaximizes the distance which the cooling fluid passes over when flowingalong the outer wall 19. There is, therefore, a maximum convectioncooling. The effect of the convection cooling is further strengthened bythe turbulators 23 because the latter improve the heat exchange betweenthe outer wall 19 and the cooling fluid.

[0036] The cooling fluid can be differentially admitted to the chambers32. This is achieved by a variation of the number and/or size of theopenings 27 of the insert 25. In this way, individual chambers 32 can,in a targeted manner, be more strongly or less strongly cooled thanothers. The cooling can therefore be adjusted in a targeted manner alongthe longitudinal center line 31 of the guide vane 13 and matched to theboundary conditions present.

[0037] The turbulators 23 are additionally used for reinforcing theouter wall 19. In this arrangement, the straight turbulators 23 arearranged in such a way that they form polygons. In FIG. 3, triangles arepresented as an example and in FIG. 6, rhombuses are presented asexamples. The reinforcement achieved by means of the turbulators 23permits a reduction in the wall thickness d of the outer wall 19 in theregion between the turbulators 23. Because of this reduction in the wallthickness d, the cooling efficiency is further increased.

[0038]FIG. 6 shows an end view onto the inside of the outer wall 19 in asecond embodiment. In this embodiment, the turbulators 24 are inclinedrelative to the longitudinal center line 31 of the guide vane 13.Because of this inclination, the length of the chambers 32 is increasedand, therefore, the efficiency of the convection cooling is increased.In this embodiment also, straight turbulators 23 are provided and fourof these are combined to form a rhombus in each case. The reduction inthe wall thickness is diagrammatically indicated in these rhombuses bymeans of visible edges.

[0039] The second outer wall 20 is also, of course, provided withcorresponding turbulators 23 and horizontal ribs 24. The horizontal ribs24 and the turbulators 23 can also be provided, alternatively oradditionally, in the case of a rotor blade 14.

[0040]FIGS. 7 and 8 show two embodiments of the insert 25. In theembodiment of FIG. 7, the cooling fluid is supplied from both ends 34,35 of the insert and emerges through the openings 27. Such an insert 25can, for example, be used in the first blading row.

[0041] As an alternative, an insert 25, which is closed at the end 34,can—as shown in FIG. 8—be provided. The cooling fluid is then onlysupplied via the end 35. This insert 25 is used in the further bladingrows, in which only one end of the guide vane 13 or of the rotor blade14 can have cooling fluid admitted to it via the casing 11 or the rotor12. Because of the horizontal ribs 24 provided according to anembodiment of the invention, there is a directed flow of the coolingfluid along the outer walls 19, 20. The cooling effect is thereforesubstantially improved. At the same time, simple manufacture is possiblebecause it is possible to dispense with blades/vanes with hollow walls.

[0042] The invention being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. A turbine blade/vane (13; 14), having at least one duct (22) which isbounded by walls (19, 20, 21), at least one wall (19, 20) having anumber of horizontal ribs (24) and outlet openings (28), an insert (25)provided with openings (27) and through which a cooling fluid can flow,being inserted into at least one duct (22), which insert (25) is at adistance from the walls (19; 20) due to the horizontal ribs (24), andtouches the latter, it being possible for the cooling fluid to emergethrough the openings (27) from the insert (25) into a chamber (32)through which the cooling fluid can flow, which chamber (32) is formedfrom the horizontal ribs (24), the insert (25) and the wall (19; 20),characterized in that the openings (27) of the insert (25) are arrangedat a first end of the chambers (32) and the cooling fluid outletopenings (28) in the wall (19; 20) are arranged at a second end of thechambers (32), and that turbulators (23) are provided between thehorizontal ribs (24) to improve the heat exchange between the wall (19;20) and the cooling fluid.
 2. The blade/vane as claimed in claim 1,characterized in that the horizontal ribs (24) are arrangedsubstantially at right angles to a longitudinal center line (25) of theblade/vane (13; 14).
 3. The blade/vane as claimed in claim 1 or 2,characterized in that the insert (25) is closed at one end (34).
 4. Theblade/vane as claimed in one of claims 1 to 3, characterized in that theturbulators (23) are used to reinforce the wall (19; 20) and merge intoone another and into the horizontal ribs (24).
 5. The blade/vane asclaimed in one of claims 1 to 4, characterized in that the turbulators(23) have a substantially straight configuration.
 6. The blade/vane asclaimed in claim 4 or 5, characterized in that the turbulators (23) arearranged in such a way that, together with the horizontal ribs (24),they form recesses adjacent to one another in the form of polygons, inparticular triangles or rhombuses.
 7. The blade/vane as claimed in claim5 or 6, characterized in that the wall thickness (d) of the wall (19;20) is reduced, at least in the region between the turbulators (23). 8.The blade/vane as claimed in one of claims 1 to 7, characterized in thatthe blade/vane is configured as guide vanes (13) or as rotor blades (14)of a turbomachine (10).